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Cas4

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Protein used in CRISPR
CRISPR-associated protein 4
Pyrobaculum calidifontis Cas4, PDB: 4R5Q​
Identifiers
Symbolcas4
PfamPF01930
InterProIPR022765
Available protein structures:
Pfam  structures / ECOD  
PDBRCSB PDB; PDBe; PDBj
PDBsumstructure summary

Cas4 is an endonuclease found in some CRISPR systems that is used as part of the spacer acquisition stage.

Geobacter sulfurreducens Cas1-Cas2-Cas4 complex bound to double stranded protospacer adjacent motif (PAM) spacer DNA. Cas1 homodimers (blue) bind to each side of the Cas2 homodimer (red) with a Cas4 Fe-S nuclease (cyan) bridging the two. The 3′ end of each DNA strand threads into the Cas4 active site. PDB: 7MI4​

Cas4 is required for efficient prespacer processing by forming a Cas4-Cas1-Cas2 complex. In this complex, Cas4 cuts double-stranded substrates with long 3'-overhangs through site-specific endonucleolytic cleavage. Cas4 closely interacts with the integrase active sites of Cas1, recognizes PAM sequences within the substrate and cleaves precisely upstream of them, ensuring the acquisition of functional spacers.

References

  1. ^ Lee H, Dhingra Y, Sashital DG (April 2019). "The Cas4-Cas1-Cas2 complex mediates precise prespacer processing during CRISPR adaptation". eLife. 8. doi:10.7554/eLife.44248. PMC 6519985. PMID 31021314.
  2. ^ Lee H, Zhou Y, Taylor DW, Sashital DG (April 2018). "Cas4-Dependent Prespacer Processing Ensures High-Fidelity Programming of CRISPR Arrays". Molecular Cell. 70 (1): 48–59.e5. doi:10.1016/j.molcel.2018.03.003. PMC 5889325. PMID 29602742.
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